a) Water droplets will be observed on Dish X. Dish X is colder than the surrounding air and therefore, water vapour in the air will lose heat to and condense on Dish X.
b) The temperature inside the air is lower (colder) than the temperature outside the car.
c) As the fan speed increases, the temperature within the car (including the windscreen) will get cooler, reducing the temperature difference between the air and the surface of the windscreen. Therefore, less heat will be lost by the water vapour to the windscreen and less condensation will occur.
(Technically, it is a lot more complicated than this and other factors will also affect the amount of condensation inside cars. It requires some understanding of humidity and how air-conditioners dehumidifies the air, which aren’t in the primary school syllabus.)